It is known in the art that photographic display materials are utilized for advertising, as well as decorative displays of photographic images. Since these display materials are used in advertising, the image quality of the display material is critical in expressing the quality message of the product or service being advertised. Further, a photographic display image needs to be high impact, as it attempts to draw consumer attention to the display material and the desired message being conveyed. Typical applications for display material include product and service advertising in public places such as airports, buses and sports stadiums, movie posters, and fine art photography. The desired attributes of a quality, high impact photographic display material are a slight blue density minimum, durability, sharpness, and flatness. Cost is also important, as display materials tend to be expensive compared with alternative display material technology, mainly lithographic images on paper. For display materials, traditional color paper is undesirable, as it suffers from a lack of durability for the handling, photoprocessing, and display of large format images.
In the formation of color paper it is known that the base paper has applied thereto a layer of polymer, typically polyethylene. This layer serves to provide waterproofing to the paper, as well as providing a smooth surface on which the photosensitive layers are formed. The formation of a suitably smooth surface is difficult, requiring great care and expense to ensure proper laydown and cooling of the polyethylene layers. The formation of a suitably smooth surface would also improve image quality as the display material would have more apparent blackness as the reflective properties of the improved base are more specular than the prior materials. As the whites are whiter and the blacks are blacker, there is more range in between and, therefore, contrast is enhanced. It would be desirable if a more reliable and improved surface could be formed at less expense.
Prior art photographic reflective papers comprise a melt extruded polyethylene layer which also serves as a carrier layer for optical brightener and other whitener materials, as well as tint materials. It would be more effective if the optical brightener, whitener materials, and tints, rather than being dispersed throughout the extruded layer of polyethylene, could be concentrated nearer the surface where they would be more effective optically.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin coated clear polyester sheet. Incorporated diffusers are necessary to diffuse the light source used to backlight transmission display materials. Without a diffuser, the light source would reduce the quality of the image. Typically, white pigments are coated in the bottommost layer of the imaging layers. Since light sensitive silver halide emulsions tend to be yellow because of the gelatin used as a binder for photographic emulsions, minimum density areas of a developed image will tend to appear yellow. A yellow white reduces the commercial value of a transmission display material because the imaging viewing public associates image quality with a white white. It would be desirable if a transmission display material with an incorporated diffuser could have a more blue white, as this is perceived as preferred.
It has been proposed in U.S. Pat. No. 5,212,053 to use a cellulose paper base with a basis weight less than 120 grams per square meter as a support for a photographic translucent display material. In U.S. Pat. No. 5,212,053 numerous advantages are obtained by the use of cellulose paper as a base. Advantages such as the low cost of paper compared to suitable polymer bases and an increase in manufacturing efficiency gained by the use of color photographic paper forming apparatus. While all of these improvements are possible with the use of a paper base, the paper base described in U.S. Pat. No. 5,212,053 does not have the required strength properties to be reliability processed in wet chemistry required in the imaging development process. When the backlighted photographic display materials are processed using photographic processing chemistry, the web can break causing a loss of materials and a reduction in the efficiency of commercial photoprocessing labs. In order to increase the strength of the paper described in U.S. Pat. No. 5,212,053 the paper would loose the desired transmission properties. It would be desirable if translucent display material with a cellulose paper base had the required strength properties to avoid breaking in photoprocessing, yet thin enough to exhibit the required transmission properties.
Prior art photographic transmission display materials with incorporated diffusers have light sensitive silver halide emulsions coated directly onto a gelatin subbed clear polyester sheet. TiO.sub.2 is added to the bottommost layer of the imaging layers to diffuse light so well that individual elements of the illuminating bulbs utilized are not visible to the observer of the displayed image. However, coating TiO.sub.2 in the imaging layer causes manufacturing problems such as increased coating coverage which requires more coating machine drying and a reduction in coating machine productivity as the TiO.sub.2 requires additional cleaning of the coating machine. Further, as higher amounts of TiO.sub.2 are used to diffuse high intensity backlighting systems, the TiO.sub.2 coated in the bottommost imaging layer causes unacceptable light scattering reducing the quality of the transmission image. It would be desirable to eliminate the TiO.sub.2 from the image layers while providing the necessary transmission properties and image quality properties.
Prior art photographic transmission display materials use polyester as a base for the support. Typically the polyester support is from 150 to 250 .mu.m thick to provide the required stiffness. A cellulose paper base material would be lower in cost and allow for roll handling efficiency, as the rolls would weigh less and be smaller in diameter. It would be desirable to use a cellulose paper base material that had the required stiffness but was thinner to reduce cost and improve roll handling efficiency.